FIG. 4 is a structural schematic view showing a conventional circuit protection device 280 comprising a PTC device and FIG. 5 is a cross-section view of FIG. 4.
In the conventional technique shown in FIGS. 4 and 5, a PTC device includes PTC materials 246 and a first metal electrode layer 248 and a second metal electrode layer 250 covering two side surfaces of the PTC materials 246, respectively.
As shown in FIGS. 4 and 5, the circuit protection device 280 includes the PTC device and a diode 244 welded to the first metal electrode layer 248 of the PTC device. One electrode of the diode 244 is electrically connected to the first metal electrode layer 248 of the PTC device and the other electrode of the diode 244 is led out by a wire 258. One electrode of the PTC device is led out by a wire 259 and the other electrode of the PTC device is formed of a portion 262 of the second metal electrode layer 250 which is uncovered. Furthermore, insulating cement 249, 251 covers the whole circuit protection device 280 except for the portion 262.
In the conventional circuit protection device shown in FIGS. 4 and 5, if overvoltage occurs in the circuit, heat generated in the diode 244 cannot be timely conducted to the PTC device, failing to cause the PTC device to timely come to a high resistance state, thus failing to timely provide the circuit with overvoltage protection.
In the conventional circuit protection device shown in FIGS. 4 and 5, it is necessary to lead out the electrodes of the PTC device and the diode by way of the wires 258, 259. Therefore, it is necessary to weld the wires 258, 259 to the electrodes of the diode and the PTC device, which can be time-consuming and labored, causing low production efficiency, thus not being suitable for mass production manufacturing.
In addition, in the conventional circuit protection device shown in FIGS. 4 and 5, the circuit protection device has a large contour and, therefore, does not have a compact structure.